mensetu ni ha kitinto sita huku wo kite ikimasu.

に marks the destination or target: to/for the interview.

は adds topic or contrast. In this sentence, 面接には gives a nuance like:

• as for interviews
• when it comes to interviews
• for an interview, at least

So 面接に行きます is a plain go to the interview, while 面接には行きます or 面接には… can sound a little more focused or contrastive.

In this sentence, 面接には helps set up the idea that for an interview, you go wearing proper clothes.

きちんとした means something like:

• proper
• neat
• tidy
• appropriate

So きちんとした服 means proper/neat clothes or appropriate attire.

It does not necessarily mean extremely formal clothing. It means clothing that is suitable and presentable for the situation.

This is a very common learner question.

きちんと is often used as an adverb, but it can also be part of the expression きちんとした + noun.

You can think of きちんとした as meaning:

• well-put-together
• proper
• tidy

Historically, this comes from きちんとする, and the した is the plain past form used before a noun, but in modern Japanese, きちんとした is best learned as a set phrase when it modifies a noun.

So:

• きちんとする = to do something properly / to be neat
• きちんとした服 = proper/neat clothes

Because 着る takes the thing you wear as its direct object.

So:

• 服を着る = to wear clothes
• シャツを着る = to wear a shirt
• スーツを着る = to wear a suit

That is why the sentence has 服を着て.

着て行きます is 着る in the て-form plus 行きます.

It means:

• go wearing
• wear ... and go
• go in ...

So the idea is not just I will put clothes on, but I will go to the interview wearing proper clothes.

This pattern is very common:

• 帽子をかぶって行きます = I’ll go wearing a hat.
• 傘を持って行きます = I’ll take an umbrella with me.

In practice, it usually gives the sense of going while wearing them, and in this sentence that is clearly the intended meaning.

So きちんとした服を着て行きます means:

• I’ll go wearing proper clothes
• I’ll wear proper clothes to the interview

English often expresses this more naturally as I’ll wear proper clothes to the interview, even though the Japanese literally looks like put on proper clothes and go.

Yes. Both are used.

• 着て行きます
• 着ていきます

They mean the same thing here. Writing it with kanji (行きます) makes the verb boundary clearer, while hiragana (いきます) is also very common.

面接 usually means a formal interview or face-to-face interview, such as:

• a job interview
• a school entrance interview
• some other official interview setting

By itself, it does not have to mean only a job interview, but that is a very common interpretation.

Because the speaker is describing movement to the interview from their current point of view.

• 行きます = go
• 来ます = come

So if I say 面接にはきちんとした服を着て行きます, I mean I go / will go to the interview wearing proper clothes.

The sentence is in polite non-past style because of 行きます.

That makes it appropriate for neutral, polite conversation or textbook Japanese.

If you changed it to plain style, it would be:

面接にはきちんとした服を着て行く。

No. In normal Japanese writing, you would usually write it without spaces:

面接にはきちんとした服を着て行きます。

Spaces are often added in beginner materials to make the sentence easier to read.